For decades, schizophrenia and bipolar disorder (BD) were treated as distinct and unrelated psychiatric disorders. Schizophrenia is a psychiatric disorder characterized by altered thinking and emotional patterns, hallucinations, false or irrational beliefs (i.e., delusions), cognitive deficits, and disorganized speech. BD, on the other hand, is marked by extreme mood swings, ranging between periods of high-energy (i.e., mania or hypomania) and depressive episodes.
While the symptoms of schizophrenia and BD are markedly different, many patients diagnosed with either of these conditions experience psychosis at least once in their lifetime. Psychosis is a mental state that causes people to lose touch with reality, experiencing hallucinations, delusions, disorganized speech, and irrational thinking patterns.
More recently, studies found that patients diagnosed with schizophrenia and BD sometimes share other overlapping symptoms, as well as common patterns in their genes and brain organization. This inspired the idea that these disorders are part of a shared psychosis spectrum, which would explain their common features and characteristics.
Researchers at University of Florence, Geneva University Hospital, and École Polytechnique Fédérale de Lausanne reviewed and analyzed the findings of previous studies to further test this hypothesis and validate the existence of a psychosis spectrum of disorders. Their paper, published in Nature Mental Health, outlines common brain features in patients with schizophrenia and BD, particularly differences in the integrity of white matter.
“This study grew out of an ongoing international collaboration aimed at better understanding mental disorders beyond traditional diagnostic labels and following our previous work on brain activity alterations in psychotic disorders,” Dr. Saccaro, co-author of the paper, told Medical Xpress.
“Over the past years, increasing evidence has shown that conditions such as schizophrenia and bipolar disorder share many biological features, including genetic risk factors and brain alterations, suggesting they may lie along a common ‘psychosis spectrum’ rather than being completely distinct illnesses.”
Most past neuroimaging studies focused on either schizophrenia or BD, rather than comparing the two. Saccaro and his colleagues analyzed data collected over the past three decades with the goal of uncovering shared brain alterations between the two disorders.
“Our main goal was to examine whether changes in white matter (the brain’s communication pathways) represent a shared feature across the psychosis spectrum, rather than disorder-specific abnormalities,” said Saccaro.
An in-depth analysis of past psychosis-related research
As part of their study, Saccaro and his colleagues systematically reviewed brain imaging data collected by different teams of neuroscience and mental health researchers over the past 30 years. All this data was collected using magnetic resonance imaging (MRI), a non-invasive imaging technique that allows scientists to obtain 3D images of the brain and infer properties of white matter connections.
“These connections act like information highways, enabling different brain regions to communicate efficiently,” explained Saccaro. “In total, we combined data from 96 studies involving thousands of participants with psychosis spectrum disorders and healthy controls. We focused on two well-established measures of white matter structure that reflect how organized and intact these brain pathways are.”
The researchers collectively analyzed the results of several studies, looking at schizophrenia and BD both individually and together, all while also accounting for differences in age and sex. This allowed them to identify brain regions that appear to be similarly affected in patients with either of the two disorders.
Most notably, they observed shared white matter alterations in a region called the corpus callosum. This is a brain structure that connects the brain’s left and right hemispheres.
“This alteration was observed across the entire psychosis spectrum, rather than being limited to a single diagnosis,” said Saccaro. “Importantly, these findings remained significant (and in some cases became clearer) after accounting for age and sex, suggesting they are unlikely to be explained simply by illness duration or aging. This supports the idea that disruptions in brain connectivity may represent a core biological feature of psychosis.” https://medicalxpress.com/news/2026-02-common-biomarker-schizophrenia-bipolar-disorder.html
Guiding the future diagnosis and treatment of psychosis
The results of this recent meta-analysis pinpoint a candidate biomarker that appears to characterize both schizophrenia and BD. The researchers’ efforts could soon inspire other teams to search for shared features between different psychiatric disorders.
These brain alterations could also help to assess the risk that individuals with develop any mental health disorder associated with psychotic episodes. In addition, this work could inform the development of new diagnostic tools, treatment strategies, or methods to predict the risk of psychotic episodes.
“Our study suggests that future interventions could be designed to target these common psychosis-related connectivity disruptions, with the potential to improve brain functioning across diagnostic categories,” said Saccaro. “In the longer term, such approaches might even help reduce the risk of development of symptoms in vulnerable individuals.”
As part of their next studies, Saccaro and his colleagues plan to review longitudinal studies that looked at how the brains of individuals who are at greater risk of experiencing psychosis develop over time. This shed light on whether the differences in white matter connections identified in this work appear before or after the first symptoms of schizophrenia or BD emerge.
“This would help clarify whether they represent an early vulnerability factor rather than a consequence of the illness itself,” added Saccaro. “Another important direction for further research will be to combine brain imaging with genetic, clinical, and cognitive data. Integrating these different levels of information could provide a more complete understanding of how psychosis develops and help to move psychiatry toward more personalized, biologically informed care.” https://medicalxpress.com/news/2026-02-common-biomarker-schizophrenia-bipolar-disorder.html
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